Question on ieee80211_tx_status
It appears that ieee80211_tx_status also scales poorly
when using large numbers of virtual stations connected
to a single AP, due to for_each_sta_info(local, hdr->addr1, sta, tmp)...
I'm going to try using the vif-hashing to make this faster, but first a question:
Since it matches on MAC addresses, should it just return at the bottom of the loop since it has found a match, and MACs are supposed to be unique?
for_each_sta_info(local, hdr->addr1, sta, tmp) {
/* skip wrong virtual interface */
if (!ether_addr_equal(hdr->addr2, sta->sdata->vif.addr))
continue;...
If so, that would be a good improvement since the hash can easily be turned into a linear search even in AP mode (without all of my virtual-station scenarios)...
Thanks,
Ben
Signature · 2 lines
Ben Greear <[email protected]> Candela Technologies Inc http://www.candelatech.com
Quoted 11 lines · Ben Greear
It appears that
ieee80211_tx_statusalso scales poorly
when using large numbers of virtual stations connected
to a single AP, due tofor_each_sta_info(local, hdr->addr1, sta, tmp)...I'm going to try using the vif-hashing to make this faster, but first a question:
Since it matches on MAC addresses, should it just return at the bottom of the loop since it has found a match, and MACs are supposed to be unique?
Quoted 5 lines
for_each_sta_info(local, hdr->addr1, sta, tmp) { /* skip wrong virtual interface */ if (!ether_addr_equal(hdr->addr2, sta->sdata->vif.addr)) continue;...
I think that'd be mostly safe, since we don't allow the same station to be added to multiple VLANs. However, I'm not entirely sure if it really is safe in the case of WDS interfaces.
Quoted 3 lines
If so, that would be a good improvement since the hash can easily be turned into a linear search even in AP mode (without all of my virtual-station scenarios)...
I don't really see how the hash could be linear? When the low byte of MAC addresses is the same, but otherwise?
johannes
Quoted 18 lines · Johannes Berg
Quoted 11 lines · Ben Greear
It appears that
ieee80211_tx_statusalso scales poorly
when using large numbers of virtual stations connected
to a single AP, due tofor_each_sta_info(local, hdr->addr1, sta, tmp)...I'm going to try using the vif-hashing to make this faster, but first a question:
Since it matches on MAC addresses, should it just return at the bottom of the loop since it has found a match, and MACs are supposed to be unique?
Quoted 5 lines
for_each_sta_info(local, hdr->addr1, sta, tmp) { /* skip wrong virtual interface */ if (!ether_addr_equal(hdr->addr2, sta->sdata->vif.addr)) continue;...
Quoted 3 lines
I think that'd be mostly safe, since we don't allow the same station to be added to multiple VLANs. However, I'm not entirely sure if it really is safe in the case of WDS interfaces.
Would you ever need to send an ACK multiple times? If so, then my approach would be wrong, but if you never should, then my approach would be more right than the current code.
It would seem to me that you should never ack a packet more than once, but I don't actually know enough about the protocol to know if that is a valid assumption.
Quoted 6 lines
Quoted 3 lines
If so, that would be a good improvement since the hash can easily be turned into a linear search even in AP mode (without all of my virtual-station scenarios)...
I don't really see how the hash could be linear? When the low byte of MAC addresses is the same, but otherwise?
Sure, just randomize octed 3 and 4 and leave octet 5 the same. Easily done in certain test tools :)
The new RFC patch I posted uses a better hash, and fixes all of the linear walk issues that show up in 'perf top' with 300 stations on a relatively weak Atom system...
Also, to deal with cases where sdata may have duplicate macs, I just added a for_each_sdata() macro that should quickly walk a hash list of sdata objects and get the same behaviour efficiently (assuming that you don't have large amounts of sdata with the same MAC, but that seems unlikely to happen).
Thanks,
Ben
Signature · 2 lines
Ben Greear <[email protected]> Candela Technologies Inc http://www.candelatech.com